The present application relates to an ultrasonic diagnostic apparatus which can execute a continuous wave Doppler (CWD)/B simultaneous mode of simultaneously displaying a Doppler spectrum image captured by CWD and a tomogram captured by the B mode in cardiac diagnosis.
Ultrasonic diagnosis allows to display in real time how the heart beats or the fetus moves, by simply bringing an ultrasonic probe into contact with the body surface. This technique is highly safe, and hence allows repetitive examination. Furthermore, this system is smaller in size than other diagnostic apparatuses such as X-ray, CT, and MRI apparatuses and can be moved to the bedside to be easily and conveniently used for examination. In addition, ultrasonic diagnosis is free from the influences of exposure using X-rays and the like, and hence can be used in obstetric treatment, treatment at home, and the like.
Recently, in cardiac diagnosis, image diagnosis called PWD (Pulse Wave Doppler)/B simultaneous mode has been executed by using such an ultrasonic diagnostic apparatus. The PWD/B simultaneous mode is a mode of executing Doppler spectrum imaging by continuous wave Doppler and B-mode tomography at a predetermined timing and displaying the captured images in real time. The PWD/B simultaneous mode includes an imaging method called interleaved scan and an imaging method called segment scan. Interleaved scan is a technique of repeatedly executing, for example, one B-mode scan per four times of execution of Doppler scan. Segment scan is a technique of alternately repeating a period (Doppler segment period) of repeating transmission/reception in the Doppler mode by a predetermined number of times and a period (non-Doppler segment period) of repeating transmission/reception in the B mode by a predetermined number of times.
The CWD/B simultaneous mode, however, requires switching of continuous waves unlike a case in which PWD is used. For this reason, a B-mode image is displayed in the freeze mode during a period in which real-time display is performed in the Doppler mode. This makes it difficult to simultaneously implement real-time display of both a Doppler spectrum and a B-mode image in the CWD/B simultaneous mode, although the implementation of such technique is clinically demanded.
In order to improve the real-time performance of the CWD/B simultaneous mode, it is necessary to solve, for example, the following two problems. One is the problem of losses in intermittent execution of continuous STFT (Short Time Fourier Transform) analysis. For example, a large loss of about 50 ms occurs per frame in B-mode images. Even if interpolation of a loss of a maximum of about 16 ms is performed for this loss, the problem of image quality deterioration occurs. The other is the problem of strong transient responses (30 ms to 100 ms) due to the necessity to instantly switch B-mode scan and Doppler-mode scan. This transient response causes noise such as spike noise in a Doppler spectrum, resulting in degrade of image quality.
It is possible to handle the problem of losses in intermittent execution of continuous STFT analysis by using the spectrum loss interpolation technique disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2001-149370, which uses an ARX model using an ECG waveform as a deterministic external input. However, there is no corresponding unit for the other problem of transient responses.